Oncogenes of special interest to the LCMB because of their possible role in human cancer are subjected to in vivo tests in appropriate mouse models. Simultaneously, the mechanisms of in vitro transformation by these oncogenes are explored. The oncogenes scrutinized this year were arg, abl, erbB-2, ras, fos, platelet-derived growth factor receptor (PDGFR), sis, ect-2, hst, tim, nep, G alpha 12, eph, int-1, erbB-3 and fbj. Each oncogene was administered by grafting cells containing it, or as c-viral recombinants, or by a combination of cellular and viral methods.